In general, a headrest is designed to be installed on the driver's seat and the passenger's seat of the vehicle to support the head of the driver or passenger so that the head can be rested while preventing the head from being tilted back and forth in sudden unintended accelerations or accidents.
In a conventional headrest, the headrest is manufactured by inserting or injecting a flexible polyurethane, which is a foam material excellent in cushioning property, into a skin material sewn using a fabric having air permeability. As shown in FIG. 1, such a headrest is made by sewing the skin material by using the fabric in a shape the same as that of the headrest, inserting a stay frame into the headrest, the stay frame having a finishing material for finishing a lower end portion of the headrest, and then injecting the flexible polyurethane foaming liquid into the skin material through an injection port at a center of the finishing material. The urethane foaming liquid injected into the skin material hardens after a certain period of time, thereby forming the shape of the headrest.
In order to ensure the user's comfort as well as his/her safety in the event of a car accident, the headrest is integrally provided with the stay frame such that cushioning function is enhanced at a portion where the user's head is rested while maintaining a certain degree of strength, such that the user's comfort and the safety can be secured at the same time. In the case of the above-described prior art, since the headrest is integrally foamed with the skin material and the stay frame, the manufacturing method is simple and the production cost is reduced. However, there is a problem in that the stability and comfort of the user are reduced because the portion where the user's head is rested has the same hardness as that of the other portions.
In an effort to solve such a problem, as shown in FIG. 2, recently, a method of manufacturing an assembly-type headrest has been proposed. The method of manufacturing the headrest is a method in which the flexible urethane (hereinafter, referred to as a “main body”) is foamed and then a cushion member is assembled to the portion where the user's head is rested. Generally, the flexible polyurethane for headrests has a density of 0.040 to 0.065 g/cm3.
However, according to the above-described conventional assembly method, a soft cushion member is used at the portion where the user's head is rested to improve the comfort and safety of the user, compared to providing a cushion member prepared by the conventional method of manufacturing the integral foam type headrest. However, there is a problem in that that it takes a much time and expense for processes after the foaming, such as finishing of the foamed the main body of the headrest, cutting of the main body, insertion of the cushion member, attaching of a tape to the cushion member, etc. In addition, since the tape must be attached to the cushion member, as shown in FIG. 3, a loosening phenomenon occurs between a headrest cover and the cushion member as illustrated in part A. Further, creasing may occur in the headrest cover, which may easily cause defective packaging, and there is a high possibility that the portion where the user's head is rested may protrude. Moreover, the assembly-type method does not provide a satisfactory effect for the passenger even when the cushion member having a thickness of equal to or greater than 15 mm is used.
Meanwhile, in recent years, in order to provide comfort and softness in addition to stability at the portion where the user's head is rested, softness properties are increasingly required as the cushion member. Accordingly, in order to satisfy such high softness, a cushion member having a thickness of equal to or greater than 10 mm is required.
However, the conventional integrated foam type headrest is problematic in that it is very difficult to attach a cushion member equal to or greater than 10 mm in thickness. In other words, when a cushion member having a thickness of equal to or greater than 5 mm is attached, the difference in elongation of a material (fabric, artificial leather, natural leather, etc.) and the cushion member is large, and thus neither can a good appearance nor a stable cushioning function be provided.
In addition, although attempts have been made to increasing the softness by increasing a thickness of a sponge used for the headrest cover, the sewing ability due to thickening of the cover becomes difficult and also appearance defects occur due to the characteristics of the integral foam type headrest. Further, the foam material is absorbed and hardened due to hygroscopicity of the cushioning member, thereby causing a phenomenon that softness of the cushioning member becomes significantly lowered over time.
Further, a sponge may be provided inside the cushion member so as to prevent the foam material from being absorbed to the cushion member. In this case, however, as shown in FIG. 5, the sponge for preventing absorption presses the cushion member at a curved part of the headrest, thereby causing creasing B, and thus softness properties at the creasing B are significantly lowered, and the passenger feels discomfort when leaning his/her head, which leads to a problem that the mass productivity and quality of the headrest are greatly deteriorated.
Vehicle headrests can be manufactured in various shapes. In particular, when the headrest is made of a curved headrest as shown in FIG. 4, the above-described problems may remarkably appear.